This proposal concerns optimization of enzymes, pores, and computational methods for single molecule sequencing of genomic DNA fragments. It is based on a proven nanopore device implemented by our group at UCSC. This device is comprised of a sensor that touches and examines each nucleotide within a captured DNA strand as a processive enzyme motor advances the strand. Although the overall goal of nanopore sequencing is de novo reads on very long strands, here we will also focus on resequencing of DNA from organisms important in basic research (mouse, E. coli & Arabidopsis) and in healthcare (human). We are focusing on both de novo and resequencing for two reasons: 1) nanopore sequencing of biological DNA has not been documented publicly. Therefore, nanopore resequencing of reference standards is required for community acceptance, and, importantly, to reveal weaknesses in the technology that impact de novo sequencing accuracy; 2) nanopore resequencing in this application means reading genomic DNA directly and therefore will include epigenetic modifications. This would be an immediate, important contribution to the research community.